PURPOSE: To irradiate electron rays on the respective sectioned irradiation regions by sectioning an object to be irradiated into a plurality of irradiation regions along the scanning direction of electron rays, and scanning the electron rays while making scanning speed of electron rays irradiating on the respective irradiation regions different.

CONSTITUTION: Provided that the carrier direction is a direction as illustrated, a carrier mechanism 3 is sectioned into two irradiation regions 6, 7 along a scanning direction and mutually having a width W. When scanning speed in the region 7 is twice as high as that in the region 6, a locus of electron rays becomes as shown by a mark D in the illustration. As clear therefrom, a dosage of irradiation electrons in the region 6 is twice as much as that in the region 7. Now, a characteristic is made memorized by a memory 8 and this is taken out every going and returning to be given to a central processing unit 9 for being amplified by a high-frequency amplifier 11 followed by exciting a scanning coil 4 by its output.